Isomerization of olefins



Patented Jan. 9, 1951 UNITED" STATES PATENT OFFICE,

2,537,283 ISOMERIZATION or OLEFINS Raymond E. Schaad, Riverside, Ill.,assignor to Universal Oil Products Company, Chicago, 111., a corporationof Delaware No Drawing. Application September 29, 1948, Serial No.51,843

I Claims.

This application is a continuation-in-part of my co-pending applicationSerial Number 706,057 filed October 2-3, 1946.

This invention relates to a process for isomerizing olefinichydrocarbons and particularly for isomerizing alkenes.

An object, of this invention is to isomerize an olefinic hydrocarbon.

Another object of this invention is to isomerize an alkene having atleast four carbon atoms per molecule.

In one embodiment, this inventionrelates to a process for isomerizingolefinic hydrocarbons which comprises contacting an olefinic hydrocarbonhaving at least four carbon atoms per molecule at conversion conditionswithan amprocess have at least four carbon atoms per molecule andinclude butylenes'pentenes, and higher molecular weight normally liquidolefins, the latter including various polymers of normally gaseousolefins. Cycloolefins such as cyclopentene, cyclohexene, and variouscycloolefins may also be used but not necessarily under the sameconditions of operation as employed with open chain olefins which mayalso be referred to as alkenes.

Catalysts useful in promoting an isomerization of olefinic hydrocarbonscomprise ammonium salts of phosphoric acids. These ammonium saltsinclude both neutral and acid salts of ortho-, pyro-, tri-, tetra-, andother polyphos phoric acids, as such, in admixture with one another andalso supported on solid carriers, such as a siliceous carrier as silica,diatomaceous earth, fullers earth, crushed porcelain, etc., and alsoalumina, charcoal, and other packing materials Which do not interferewith the desired catalytic activity of an ammonium phosphate. Compositesof an ammonium salt of an acid of phosphorus and a carrier, such asdiatomaceous earth or some other siliceous material, are preferablycalcined before being utilized as catalysts in conversion reactions oforganic compounds and particularly of hydrocarbons. Such calcination isgenerally carried out at a temperature of about 200 to about 500 C.

According to the process of the present inven--' tion, an olefinichydrocarbon may be-reacted in the presence of an ammonium phosphatecatalyst at a temperature of from about C. to about 450 C. to produceisomeric olefins including branched chain and straight chain olefins.The isomerization of a straight chain olefinic in the presence of anammonium phosphate yields a branched chain olefin as a result ofso-called, skeletal isomerization of the charged olefinic .hy-

,drocarbons. The isomerization reaction .may

also involve the shifting of the position of the double bond along thecarbon chain of the olefinic hydrocarbon. Thus a shift of the doublebondoccurs when l-butylene is converted into 2- butylene whereas skeletalisomerization occurs;

during the conversion of either of the straight chain olefins,l-butylene and Z-butylene, into the branched chain olefin isobutylene,this being an example of the so-called skeletal isomerization- Olefinisomerization in the presence of acatalyst comprising an ammoniumphosphate as its essential active ingredient, is carried out preferablyat a temperature of from about 150 to about 350 0., particularly sincethe higher tem-- perature of the broader range, namely, from about 150to about 450 C., sometimes result in certain amountsof decomposition,cracking, and.

hydrogen transfer reactions. The process is also carried out generallyat atmospheric pressure,

although higher conversions may sometimes be obtained at subatmosphericpressure while increased capacity results when the process is effectedat a slight superatmospheric pressure which is generally not more thanabout 5 atmospheres. At a superatmospheric pressure; a certain amount ofolefin polymerization takes place with the result that the yield ofisomerized olefin is decreased.

The process of the present invention is carried out in either batch orcontinuous types of operation. Thus in a simple batch type process, theolefin containing at least four carbon atoms per molecule is brought toa reaction temperature as specified above in the presence of an ammoniumphosphate or of a solid composite of an ammonium phosphate and asuitable carrier 'or supporting material while the reaction mixture isstirred mechanically to eiiect intimate contact between the catalyst andthe olefinic 56, hydrocarbon charging stock.

1. A PROCESS FOR ISOMERIZING OLEFINIC HYDROCARBONS WHICH COMPRISESCONTACTING AN OLEFINIC HYDROCARBON HAVING AT LEAST FOUR CARBON ATOMS PERMOLECULE AT ISOMERIZING CONDITIONS WITH AN AMMONIUM PHOSPHATE.